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import {execSync} from 'node:child_process';
import * as fs from 'node:fs';
import * as net from 'node:net';
import * as os from 'node:os';
import * as path from 'node:path';
import {describe, it} from 'vitest';

describe('HeaptrackWrapper FD behavior tests', () => {
    it('should verify net.Socket properly handles external FDs', async () => {
        // This test verifies that net.Socket can handle external FDs and properly goes through its close sequence.
        // This is critical for HeaptrackWrapper which creates sockets from pipe FDs.

        if (process.platform === 'win32') {
            return;
        }

        const tmpDir = os.tmpdir();
        const pipePath = path.join(tmpDir, `test_pipe_${process.pid}_${Date.now()}`);

        try {
            // Create a named pipe (exactly like HeaptrackWrapper does)
            execSync(`mkfifo "${pipePath}"`);

            // Open the pipe with O_NONBLOCK (like HeaptrackWrapper does)
            const O_NONBLOCK = fs.constants.O_NONBLOCK; // Use fs.constants for portability
            const O_RDWR = fs.constants.O_RDWR;
            const fd = fs.openSync(pipePath, O_RDWR | O_NONBLOCK);

            // Create a net.Socket with the pipe FD (like HeaptrackWrapper)
            const socket = new net.Socket({fd: fd, readable: true, writable: true});

            // Set up close event listener
            const closePromise = new Promise<void>(resolve => {
                socket.on('close', () => {
                    // Close event fired - this means the socket went through its complete cleanup sequence
                    resolve();
                });
            });

            // Destroy the socket (like HeaptrackWrapper does)
            socket.destroy();

            // Wait for close event to fire
            await closePromise;

            // Success! The socket properly handled the external FD and completed its close sequence. We assume
            // (based on manual testing) that this includes closing the FD. We NEVER attempt to verify the FD
            // state ourselves to avoid FD recycling race conditions.
        } finally {
            // Clean up the pipe
            try {
                fs.unlinkSync(pipePath);
            } catch {
                // Ignore cleanup errors
            }
        }
    });
});
